The present inventions relate to mixers. More particularly, the present inventions relate to mixers that are equipped with gas injection devices and/or baffle plates to improve mixing in a variety of applications, including but not limited to water and wastewater treatment applications.
There are numerous available mixers for water and wastewater treatment applications. Of particular applicability to the present inventions are floating vertical shaft downflow mixers. Typical devices are shown and described in U.S. Pat. Nos. 4,723,848; 4,442,771 and 2,991,983 (all incorporated herein by reference). In general, such mixers include an annular float to support the mixer on the body of fluid to be mixed. A drive motor is mounted on the top of the float above the surface of the fluid. A propeller or drive shaft is connected to the drive motor and extends downwardly therefrom below the float and into the fluid. A propeller or impeller is attached to the drive shaft. A draft tube is typically mounted to the underside of the float extending downward from the float which encases the propeller. The draft tube is also provided with an intake at its upper end which is near the bottom of the float and a lower end that forms a discharge. When in use, operation of the propeller causes the fluid to be drawn into the intake in a pumping action. The fluid is then forced through the draft tube discharge end to mix the bulk fluid contents.
Other types of mixers are also known, including those that inject oxygen or other gases into the fluid body. Some such devices are shown and described in U.S. Pat. Nos. 6,145,815; 6,135,430 and EP0252903. Such known devices that inject gas as part of the mixing process typically include hoods and other mechanical arrangements that are more complicated and expensive than typical downflow mixers.
There is a need to improve the performance of typical downflow mixers, as well as to incorporate gas injection capabilities into such mixers. The present inventions are directed to such needs. In fact, the present inventions have led to unexpected results in their various combinations.